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Shocking Heart Deaths: Why They Happen

Sudden cardiac arrest isn't the same as a heart attack.

What Is Sudden Cardiac Arrest? continued...

Ventricular fibrillation disrupts the heart's pumping action, stopping blood flow to the rest of the body. A person in sudden cardiac arrest will collapse suddenly and lose consciousness, with no pulse or breathing.

Without immediate CPR or a shock from an automated defibrillator, the person usually dies within minutes -- that's why it's called "sudden cardiac death."

There is a connection between heart attack and sudden cardiac death, however. A heart attack can trigger an electrical malfunction that can lead to sudden cardiac arrest.

Causes of Sudden Cardiac Arrest

You probably know that high blood pressure, high cholesterol, diabetes, and other problems can lead to heart disease in older people. But you may not know about the rare heart disorders that can cause sudden cardiac arrest in young people.

"The underlying conditions in young people are very different from the underlying conditions in somebody who is 50 or 60 years old," Lawless says. "In the younger people, we're looking for inherited diseases of the myocardium [the heart's muscular tissue], of the electrical system, and then of course, congenital [heart] diseases."

The No. 1 culprit: hypertrophic cardiomyopathy (HCM), a disorder marked by abnormal thickening of the heart muscle. "Their heart is thick," Lawless says. "The inner layers of the heart maybe are not getting enough blood supply with exercise."

But remember, HCM is rare. It has been estimated to affect only 0.05% to 0.2% of the population.

Congenital abnormalities of the coronary arteries pose another risk for sudden cardiac arrest. The arteries may be positioned improperly -- or, as in basketball star Pete Maravich's case, a person may be born with only one coronary artery, instead of the usual two.

Other conditions that can trigger sudden cardiac arrest include an inherited electrical disorder of the heart called long QT syndrome; an inflammatory heart condition called acute myocarditis; and Marfan syndrome, which led to Flo Hyman's cardiac arrest.

Marfan syndrome is a genetic disorder of the connective tissue that can have fatal cardiovascular effects. People with Marfan syndrome "tend to be tall and lanky," Lawless says. They are at risk for tears in their blood vessels (such as the aorta). That risk rises with sudden increases in blood pressure, as may happen during intense sporting activity.

Some athletes die after being struck in the chest, a trauma called commotio cordis.

"When the chest is hit at the vulnerable period of the cardiac cycle, the heart goes into this terrible rhythm, the ventricular fibrillation," Lawless says. The chance of this happening is incredibly small since the vulnerable time window is miniscule, she says. "It's got to happen within forty-thousandths of a second."